Ozone Levels Exceeding Permitted Levels

Context: Recently, a Centre for Science and Environment (CSE) study has found that ozone levels are exceeding the permitted levels even during winter in Delhi-NCR, making the smog more “toxic”.
Issue

• Ozone is now a round-the-year problem requiring urgent action.
• The situation demands refinement of a clean air action plan to add strategies for ozone mitigation, with stronger action on vehicles, industry and waste burning.
• Ozone, a highly reactive gas and dangerous for those suffering from respiratory conditions and asthma, is becoming more widespread in Delhi and NCR across all seasons.

Key Findings

• Contrary to the notion that ozone is predominantly a summer phenomenon, the study found ozone levels exceeding the permitted levels even during winter in Delhi-NCR.
• The study notes that despite the lockdown, more days and locations witnessed a higher and longer duration of ozone spells.
• The study shows that the Ozone levels are found to be exceeding the mark of 100 μg/m3 even during winter and are highly sensitive to solar radiation. Reducing the gases will also reduce secondary particles formed from these gases.

Key Recommendations

• It is important to calibrate AQI (Air Quality Index) to report the most polluted eight-hour average of the day, ideally making it an hourly alert. Also the current practice of only city averaging needs to change to include alerts based on the worst affected area as is the global good practice.
• There needs to be a refinement of clean air action plan to add strategies for ozone mitigation, with strong action on vehicles, industry and waste burning which constitute the major sources of NOx and VOC.

Some of the strategies could involve the following

• Vapour recovery nozzles at the petrol pumps to reduce refuelling emissions
• Cleaner burning fuels reformulated to reduce VOC, NOx and other pollutants
• Strict NOx emission limits for power plants and industrial combustion sources
• Enhanced vehicle inspection programs and
• Strict limitations on solvent usage in factories.

Additional Information
Ozone

• It is a gas that occurs both in the Earth’s upper atmosphere and at ground level. Ozone can be “good” or “bad” for health and the environment, depending on its location in the atmosphere.
• While stratospheric ozone protects living things from ultraviolet radiation from the sun, ground-level ozone is considered a pollutant given the adverse health problems it gives rise to.

Ozone formation

• Ozone is a secondary pollutant. Tropospheric, or ground-level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight (photochemical reaction).
• Emissions from cars, power plants, refineries, chemical plants, and other sources are the major sources of NOx and VOC.
• Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments.

Ozone Harmful effects

• Ozone is a highly reactive gas and when inhaled it can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and, throat irritation. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.
• Elevated exposure to ozone can affect sensitive vegetation and ecosystems. In particular, ozone can harm sensitive vegetation during the growing season.